The present invention relates to a semiconductor processing apparatus for improved semiconductor wafer handling for face-down processing applications.
It is very important in semiconductor manufacturing that a minimum number of particles be introduced onto the surface of the semiconductor wafer during processing. In most semiconductor manufacturing the machines, apparatus, or tools used in manufacture do not directly contact the front surface or front-side of the wafer where the integrated circuits are formed. In general these semiconductor processing tools handle the wafers by contacting the back surface or backside during wafer transport and processing. Some processes such as chemical mechanical polishing (CMP) however do not readily lend themselves to handling the wafers by the backside only and in these processes contact is made to front-side of the wafer during processing.
Shown in FIG. 1 is a typical scheme used to handle wafers during the CMP process. In FIG. 1(a) the wafer 10 is loaded from a cassette unto the pedestal front-side down by a robot arm. The cassette and robot are not shown for clarity. The front-side 20 of the wafer 10 is in contact with the pedestal 30 and is held in place by vacuum. In operation, the pedestal moves up along the AAxe2x80x2 axis before wafer loading to stage the backside 15 of the wafer 10 for transfer to the wafer handler 40. The wafer 10 is held against the surface of the wafer handler by a vacuum during wafer processing. After loading the wafer 10 unto the wafer handler 40 the wafer handler moves along the path BBxe2x80x2 to begin CMP of the surface 20 of the wafer 10. In this type of scheme the surface 20 of the wafer 10 is polished front-side down. Although the backside 15 of the wafer 10 is held against the wafer handler 40 during the actual polishing, the pedestal 30 contacts the front-side 20 of the wafer during transport too and from the wafer handler 40.
A top view of the pedestal 30 is shown in FIG. 1(b). Also shown in FIG. 1(b) are holes 60 in the surface of the pedestal where nitrogen, water, or a vacuum can be applied to the surface of the wafer. During the wafer transfer process up to 80% of the front-side 20 surface of the wafer comes into contact with the pedestal. This allows particles to be transferred to the surface of the wafer after CMP that results in diminished wafer yields of functional integrated circuits. There is therefore a need for improved semiconductor apparatus or tools that reduce the tool contact with the front-side of the wafer during transport and/or processing.
The instant invention comprises an improved semiconductor wafer handler. In a first embodiment of the instant invention the improved wafer handler comprises a ring with an upper surface and orifices for applying a vacuum to the surface of a semiconductor wafer. The ring is attached to a hub through spokes that are affixed at either end to the ring and the hub. There are orifices in the spokes through which water and nitrogen can be passed unto the surface of said semiconductor wafer. In a further embodiment a diverter valve is contained in the hub.
In a further embodiment of the instant invention a CMP processing tool with improved wafer handling comprises a wafer handler for holding a semiconductor wafer while processing and a pedestal for loading and unloading the semiconductor wafer to the wafer handler. The pedestal further comprises a ring with an upper surface and orifices for applying a vacuum to the surface of a semiconductor wafer. The ring is attached to a hub by spokes that contain orifices through which water and nitrogen can be passed onto the surface of a semiconductor wafer.
In a further embodiment the improved wafer handler further comprises a diverter valve comprising a housing with an internal top surface and an internal bottom surface and a valve ring contained in the housing such that the valve ring moves to the internal bottom surface on the application of a vacuum in the housing. In addition the diverter valve further comprises a plurality of tubes connected to the internal bottom surface such that the valve ring covers the plurality of tubes when a vacuum is applied to the housing.